Illuminated signs whether they are used indoors or outdoors are intended to provide high visibility at all hours of the day and principally at night. The traditional method has been to construct a box-like metallic frame with one or two message-carrying faces made from translucent glass or plastic material. Illumination is provided by strong lights built inside the box-like frame. The message is usually changed by either replacing the entire translucent faces or by substitution of removable types which adhere to the illuminated faces. Outdoor signs which require a large message area and indoor signs of more than one square meter of display surface require elaborate structural framework in order to support the display surface material, and to withstand the action of the wind. As a result this type of sign is seldom movable. Marquee-type illuminated signs which are installed on the faces of buildings also require elaborate anchoring and supporting frameworks thich render them expensive to install and difficult to modify.
All these drawbacks make it practically impossible to construct temporary or highly mobile illuminated signs of any size suitable for outdoor use.